answers for day 9

09/code.js

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+const fs = require('fs');
+
+//const inputArray = fs.readFileSync('sample.txt').toString().split("\n");
+const inputArray = fs.readFileSync('input.txt').toString().split("\n");
+
+// Part One
+
+const head = [[0, 0]];
+const tail = [[0, 0]];
+
+for (i in inputArray) {
+  const contents = inputArray[i].split(" ");
+  const dir = contents[0];
+  const dist = contents[1];
+
+  for (m = 1; m <= dist; m++) {
+    let hx = head[0][0];
+    let hy = head[0][1];
+    let tx = tail[0][0];
+    let ty = tail[0][1];
+
+    if (dir === 'U') {
+      hy++;
+    } else if (dir === "D") {
+      hy--;
+    } else if (dir === "L") {
+      hx--;
+    }  else if (dir === "R") {
+      hx++;
+    }
+
+    head.unshift([hx, hy]);
+    tail.unshift(walk(hx, hy, tx, ty));
+  }
+}
+
+let strings = [];
+for (pos of tail) {
+  strings.push(pos.join('-'));
+}
+let touched = [...new Set(strings)];
+
+console.log(touched.length);
+
+// Part Two
+
+const h = [[0, 0]];
+const one = [[0, 0]];
+const two = [[0, 0]];
+const three = [[0, 0]];
+const four = [[0, 0]];
+const five = [[0, 0]];
+const six = [[0, 0]];
+const seven = [[0, 0]];
+const eight = [[0, 0]];
+const t = [[0, 0]];
+
+for (i in inputArray) {
+  const contents = inputArray[i].split(" ");
+  const dir = contents[0];
+  const dist = contents[1];
+
+  for (m = 1; m <= dist; m++) {
+    let hx = h[0][0];
+    let hy = h[0][1];
+
+    if (dir === 'U') {
+      hy++;
+    } else if (dir === "D") {
+      hy--;
+    } else if (dir === "L") {
+      hx--;
+    }  else if (dir === "R") {
+      hx++;
+    }
+
+    h.unshift([hx, hy]);
+    one.unshift(walk(hx, hy, one[0][0], one[0][1]));
+    two.unshift(walk(one[0][0], one[0][1], two[0][0], two[0][1]));
+    three.unshift(walk(two[0][0], two[0][1], three[0][0], three[0][1]));
+    four.unshift(walk(three[0][0], three[0][1], four[0][0], four[0][1]));
+    five.unshift(walk(four[0][0], four[0][1], five[0][0], five[0][1]));
+    six.unshift(walk(five[0][0], five[0][1], six[0][0], six[0][1]));
+    seven.unshift(walk(six[0][0], six[0][1], seven[0][0], seven[0][1]));
+    eight.unshift(walk(seven[0][0], seven[0][1], eight[0][0], eight[0][1]));
+    t.unshift(walk(eight[0][0], eight[0][1], t[0][0], t[0][1]));
+  }
+}
+
+strings = [];
+for (pos of t) {
+  strings.push(pos.join('-'));
+}
+touched = [...new Set(strings)];
+
+console.log(touched.length);
+
+// functions
+
+function walk(hx, hy, tx, ty) {
+  if ((hx > tx) && Math.abs(hx - tx) >= 2) {
+    tx++;
+    if (hy > ty) {
+      ty++;
+    } else if (ty > hy) {
+      ty--;
+    }
+  } else if ((tx > hx) && Math.abs(tx - hx) >= 2) {
+    tx--;
+    if (hy > ty) {
+      ty++;
+    } else if (ty > hy) {
+      ty--;
+    }
+  } else if ((hy > ty) && Math.abs(hy - ty) >= 2) {
+    ty++;
+    if (hx > tx) {
+      tx++;
+    } else if (tx > hx) {
+      tx--;
+    }
+  } else if ((ty > hy) && Math.abs(ty - hy) >= 2) {
+    ty--;
+    if (hx > tx) {
+      tx++;
+    } else if (tx > hx) {
+      tx--;
+    }
+  }
+
+  return [tx, ty]
+}

09/sample.txt

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+R 5
+U 8
+L 8
+D 3
+R 17
+D 10
+L 25
+U 20